To increase their maneuverability, vehicles known from engineering practice are built with so-termed torque-vector systems, by way of which a drive torque from a drive engine in a drive train can be distributed in a controlled manner in the area of a driven vehicle axle in the transverse direction of the vehicle between the drive wheels of a driven vehicle axle, for example, the front axle or a rear axle of the vehicle. This enables the yaw behavior of a vehicle to be influenced as necessary by an asymmetric distribution of the drive torque from the engine in the transverse direction of the vehicle as a function of the driving situation prevalent at the time.
To distribute the drive torque of an engine in the transverse direction of the vehicle between two wheels of a vehicle axle, torque-vector systems are used in the area of the vehicle axle, which are made as overlap gears. With overlap gears, it is possible, by way of appropriate mechanical means, to superimpose a torque difference over the mechanically predetermined symmetrical basic distribution, whereby a yaw torque can be imposed on the vehicle independently of the intrinsic drive torque of the vehicle. The result is that the steering of the vehicle round a curve can be supported, if necessary, or a yaw torque affecting the vehicle can be damped.
Such an overlap gear is known from US 2005/0070391 A1 in which the torque difference between the wheels of a driven vehicle axle can be adjusted by hydraulic means.
In general, however, overlap gears are of disadvantageously elaborate design, characterized by a large number of components and also taking up considerable structural space and having high intrinsic weight.
Alternatively, however, the drive torque in the area of a vehicle axle can be distributed in the transverse direction of the vehicle in accordance with the operating situation and symmetrically between the wheels, by way of so-termed clutch gears of simple design. In clutch gear systems, between a conventional transverse distributor gear and each wheel, a respective frictional shift element is arranged. To impose a desired yaw torque, the wheels are acted upon individually by a predefined fraction of the drive torque so that the degree of distribution of the drive torque in the transverse direction of the vehicle varies as a function of the respectively set transmission capacity of the shift elements.
However, such clutch gear systems have the disadvantage that the maximum yaw torque that can be produced to support the cornering of a vehicle depends on and is limited by the currently available drive torque from the engine.
Therefore, the purpose of the present invention is to provide a method for operating a vehicle drive train, by way of which the desired yaw torque can be produced with a clutch gear system of simple structure.